LONGEVITY STUDY SHOWS COUNTRY FOLK ARE THE SMARTER ONES

Since the turn of the century, most people have left farms to settle in big cities. But those who stayed behind in rural areas and small towns may have reaped a big bonus: longer life.

A nationwide study of people living in major urban areas, suburbs and rural areas found that city dwellers, irrespective of where they live in a city or their economic and educational status, are 62 percent more likely to die than rural people, especially as a result of cancer and infections. This was based on deaths that occurred in the survey group during 1986-94.

The reason for the higher death rate seems to be that city residents are bigger risk takers, said James S. House of the University of Michigan Survey Research Center. City folk are more likely than farmers to smoke, drink heavily, be underweight and be less physically fit, he reported in the American Journal of Public Health.

Another surprising finding is that suburban blacks have a higher death rate than blacks who live in the city, suggesting that many of the suburbs may be as bad or worse for their longevity than inner-city neighborhoods, House said.

ENZYME LOOKS LIKE FAT VILLAIN

An obscure enzyme may play a major role in making a person fat and even in spreading cancer, according to researchers at the University of California at San Francisco. The enzyme, called plasma kallikrein, is described in the journal Nature Cell Biology, and it may make a promising target for new treatments to prevent obesity. Once thought to be important for making blood clot, the researchers have discovered that isn't really the enzyme's job.

"Its real job seems to be in making plasmin active," said Zena Werb, senior author of the paper. Plasmin is an enzyme that dissolves clots. "We've shown it is certainly crucial for allowing fat cells to develop, and it may be important in the cancer process."

People who lack the gene to produce plasma kallikrein appear to be perfectly healthy, she said. That suggests that a drug that interfered with the enzyme to block its fat-promoting activity probably wouldn't cause damaging side effects.

Because of the way the enzyme works, researchers suspect it promotes the spread of cancer cells, though they have yet to prove that. "What we are really hoping is that drugs against this enzyme may also modify cancer," Werb said. "That's where our research is heading."